Norwegian is the only major cruise line to offer year-round, roundtrip-Honolulu cruises on its American-flagged ship. Small ship line Un-Cruise Adventures offers seasonal sailings 'round the islands. Carnival. Princess. Celebrity and Holland America offer seasonal Hawaii cruises roundtrip from various California ports. Royal Caribbean offers occasional repositioning cruises to the islands, and luxury lines may call in the islands on longer Pacific crossings or world cruises.